Infants with congenital heart disease and congestive heart failure frequently experience failure to thrive. In addition to the symptoms and limitations imposed by the cardiovascular malformation, the child with delayed physical development may also lag in the development of mental and motor skills. The goal of surgery in infants and children with congenital heart disease is not only the saving of life but also prevention of the adverse effects of congenital heart disease on growth and intellectual and psychological development. An accurate estimate of energy expenditure of patients with left-to-right intracardiac shunts with or without congestive heart failure would be helpful in planning surgical procedures and optimizing nutritional support. The purpose of the proposed research is to determine the effect of left to right shunting on the total daily energy expenditures and the proportion of that total expended on basal metabolic processes in a group of 3-4 month old infants and group of healthy age-matched controls. Knowledge of the energy expenditures of these patients is necessary to accurately gauge their energy requirements, provide optimal nutritional support and optimize the timing of surgical correction. Infants will be studied before and after surgery to examine changes in these parameters brought about by surgical repair.